Overview
TVirtualDBData is a virtual data class that links TDataSet or TDataSource fields to a TeeGrid. It provides automatic integration with database components, allowing seamless display and editing of database records.
Setting the TeeGrid DataSource property to a TDataSet or TDataSource component will automatically create a TVirtualDBData object.
Usage
Automatic Creation
The simplest way to use TVirtualDBData is to assign a dataset or data source directly to the grid:
// Using TDataSet
TeeGrid1.DataSource := FDMemTable1;
// Using TDataSource
TeeGrid1.DataSource := DataSource2;
Manual Creation
You can also manually create and configure a TVirtualDBData instance:
uses Tee.GridData.DB;
// From TDataSource
TeeGrid1.Data := TVirtualDBData.From(DataSource1);
// From TDataSet
TeeGrid1.Data := TVirtualDBData.From(MyDataSet1);
Types
TVirtualFetchMode
Controls how records are fetched from the dataset:
Automatic - Automatically determines fetch strategy based on dataset characteristicsAll - Fetches all records at oncePartial - Fetches records on-demand (virtual mode)
Properties
Provides read-only access to the underlying TDataSet being displayed in the grid.var
RecordCount: Integer;
begin
if Assigned(TVirtualDBData(TeeGrid1.Data).DataSet) then
RecordCount := TVirtualDBData(TeeGrid1.Data).DataSet.RecordCount;
end;
FetchMode
TVirtualFetchMode
default:"Automatic"
Controls the record fetching strategy. Set to All for smaller datasets or Partial for large datasets to improve performance.var
DBData: TVirtualDBData;
begin
DBData := TVirtualDBData.From(FDQuery1);
DBData.FetchMode := TVirtualFetchMode.Partial; // Virtual mode for large datasets
TeeGrid1.Data := DBData;
end;
Determines whether the TVirtualDBData instance owns and will free the associated dataset. Set to True if you want the data adapter to manage the dataset’s lifetime.var
DBData: TVirtualDBData;
begin
DBData := TVirtualDBData.From(MyDataSet);
DBData.OwnsData := True; // TVirtualDBData will free MyDataSet
TeeGrid1.Data := DBData;
end;
Methods
Class Methods
Creates a TVirtualData instance from a TComponent (TDataSet or TDataSource).Signature:class function From(const ASource: TComponent): TVirtualData; override;
ASource - A TDataSet or TDataSource component
Returns:
A new TVirtualDBData instance configured for the given data source.Example:uses Tee.GridData.DB;
var
GridData: TVirtualData;
begin
GridData := TVirtualDBData.From(FDQuery1);
TeeGrid1.Data := GridData;
end;
Links a TeeGrid column to a specific TField from the dataset.Signature:class procedure LinkTo(const AColumn: TColumn; const AField: TField); static;
AColumn - The TColumn to linkAField - The TField to link to the column
Example:var
Col: TColumn;
begin
Col := TeeGrid1.Columns.Add;
TVirtualDBData.LinkTo(Col, MyDataSet.FieldByName('CustomerName'));
end;
Instance Methods
Automatically adds columns to the grid based on the dataset fields.Signature:procedure AddColumns(const AColumns: TColumns); override;
AColumns - The columns collection to populate
Example:var
DBData: TVirtualDBData;
begin
DBData := TVirtualDBData.From(FDQuery1);
TeeGrid1.Data := DBData;
DBData.AddColumns(TeeGrid1.Columns); // Manually add columns
end;
Retrieves the floating-point value of a cell.Signature:function AsFloat(const AColumn: TColumn; const ARow: Integer): TFloat; override;
AColumn - The column to read fromARow - The row index
Returns:
The cell value as a floating-point number. Retrieves the string representation of a cell value.Signature:function AsString(const AColumn: TColumn; const ARow: Integer): String; override;
AColumn - The column to read fromARow - The row index
Returns:
The cell value as a string. Returns the total number of rows (records) in the dataset.Signature:function Count: Integer; override;
Returns the RTTI type information for a column’s data type.Signature:function DataType(const AColumn: TColumn): PTypeInfo; override;
AColumn - The column to query
Returns:
Pointer to the type information for the column’s field type. Loads or reloads the grid columns from the dataset.Signature:procedure Load(const AColumns: TColumns); override;
AColumns - The columns collection to load into
Determines if a column is read-only based on the field properties.Signature:function ReadOnly(const AColumn: TColumn): Boolean; override;
AColumn - The column to check
Returns:
True if the column’s field is read-only, False otherwise. Sets a cell value, updating the underlying dataset field.Signature:procedure SetValue(const AColumn: TColumn; const ARow: Integer; const AText: String); override;
AColumn - The column to updateARow - The row indexAText - The new value as a string
Example:var
DBData: TVirtualDBData;
begin
DBData := TVirtualDBData(TeeGrid1.Data);
DBData.SetValue(TeeGrid1.Columns[0], 5, 'New Value');
end;
Calculates the optimal column width based on the data and painter.Signature:function AutoWidth(const APainter: TPainter; const AColumn: TColumn): Single; override;
APainter - The painter used for measuring textAColumn - The column to measure
Returns:
The calculated optimal width in pixels. Called when the grid enters or exits edit mode.Signature:procedure EditMode(const AMode: TEditMode); override;
AMode - The edit mode state
Refreshes the grid data from the dataset.Signature:procedure Refresh; override;
var
DBData: TVirtualDBData;
begin
DBData := TVirtualDBData(TeeGrid1.Data);
DBData.Refresh; // Reload data from dataset
end;
Complete Examples
Basic Database Grid
uses
VCLTee.Grid, Tee.GridData.DB, FireDAC.Comp.Client;
procedure TForm1.FormCreate(Sender: TObject);
begin
// Automatic - just assign the dataset
TeeGrid1.DataSource := FDQuery1;
end;
Advanced Configuration
uses
VCLTee.Grid, Tee.GridData.DB, FireDAC.Comp.Client;
procedure TForm1.SetupGrid;
var
DBData: TVirtualDBData;
begin
// Create data adapter
DBData := TVirtualDBData.From(FDQuery1);
// Configure for large dataset
DBData.FetchMode := TVirtualFetchMode.Partial;
// Assign to grid
TeeGrid1.Data := DBData;
// Customize appearance
TeeGrid1.Columns[0].Width := 200;
TeeGrid1.Columns[1].Visible := False;
end;
Master-Detail Grids
uses
VCLTee.Grid, Tee.GridData.DB;
procedure TForm1.SetupMasterDetail;
begin
// Master grid
MasterGrid.DataSource := MasterDataSet;
// Detail grid
DetailGrid.DataSource := DetailDataSet;
// Link via dataset relationship
DetailDataSet.MasterSource := MasterDataSource;
DetailDataSet.MasterFields := 'CustomerID';
end;
Custom Field Linking
uses
VCLTee.Grid, Tee.GridData.DB, Tee.Grid.Columns;
procedure TForm1.CreateCustomColumns;
var
DBData: TVirtualDBData;
Col: TColumn;
begin
DBData := TVirtualDBData.From(MyDataSet);
TeeGrid1.Data := DBData;
// Manually create and link columns
TeeGrid1.Columns.Clear;
Col := TeeGrid1.Columns.Add;
Col.Text := 'Customer';
TVirtualDBData.LinkTo(Col, MyDataSet.FieldByName('CustomerName'));
Col := TeeGrid1.Columns.Add;
Col.Text := 'Total';
TVirtualDBData.LinkTo(Col, MyDataSet.FieldByName('OrderTotal'));
end;
See Also
